At the close of the voting day, count the letters and compare them to the official tally.
Not very scientific, but IF we could pull this off ... we'd get a clearer picture of the number of voters AND whether they claimed to be conservative or not.
I know, there are conservative D's ... THEY can drop an R just for the experiment.
Since almost everyone is carrying a camera now-a-days, how hard will it be to actually count how many people entered a poling place? Why do you think they focused on mail in ballots...duh!